Conventional latch devices are for instance used in semi-conductor components (such as memory components, for instance DRAMs (DRAM=Dynamic Random Access Memory and/or Dynamic Read/Write Memory)) for the storage and/or interim storage of data, which can then be output again, for instance synchronously with a clock pulse (clk signal) used on the semi-conductor component.
State-of-the-art latch devices may for instance consist of two transfer gates and four inverters.
The input of the first transfer gate is connected to a data-input line, by means of which the data to be latched (by means of a corresponding data-input signal (data signal)) is input into the latch device. A first control connection of the first transfer gate is connected to a (first) clock line on which the clock pulse (clk signal) is present, and a further—inverse—control connection of the first transfer gate to a (further) clock line, on which a clock pulse (bclk signal), inverse to the clock pulse (clk signal) is present.
The output of the first transfer gate is connected to the input of the first inverter. The output of the first inverter is connected to the input of the second transfer gate, and to the input of the second inverter, of which the output is back connected to the input of the first inverter.
The (first) control connection of the second transfer gate is—correspondingly inverse as with the first transfer gate—connected to the above further inverse clock line (on which—as described above—the inverse clock pulse (bclk signal) is present), and the (further)—inverse—control connection of the second transfer gate is—again correspondingly inverse to the first transfer gate—connected to the first clock line (where —as described above—the clock pulse (clk signal) is present).
The output of the second transfer gate is connected to the input of the third inverter. The output of the third inverter is connected to the input of the fourth inverter, of which the output is back connected to the input of the third inverter, as well as to a data output line, by means of which the data—in latched form—that has been input into the latch device (and/or the above data-input line) can be output again synchronously with the clock pulse (clk signal)(by means of a corresponding data output signal (ldata signal)).
The data to be input into the latch device (data signal) must have been present in a stable state on the data input line for a predetermined time ahead of a corresponding (e.g. positive) flank of the clock pulse (clk signal) (and/or of a corresponding (e.g. negative) flank of the inverse clock pulse (bclk signal)), (the so-called “setup” time (Tsetup) to ensure fault-free latching of the data.
In addition, to ensure fault-free latching of the data, it must also have been present in a stable state up to a pre-determined time after the corresponding (positive) flank of the clock pulse (clk signal) (and/or of the corresponding (negative) flank of the inverse clock pulse (bclk signal)) (the so-called “hold” time (Thold)).
The “set-up” and “hold” times may—in total—be of a duration of ca. 50 to 200 picoseconds, which may be problematic, particularly at high frequencies and/or for the “critical path” that determines the efficiency of all the semi-conductor components.
The above “set-up” and “hold” times could be reduced if it could be ascertained that the clock—and the inverse clock pulses (clk and bclk signals)—were completely complementary to one another (and that they would not change their states at times minimally varying from each other, from “high logic” to “low logic” (negative flank) and correspondingly inverted from “low logic” to “high logic” (positive flank).
This goal is however not at all, or only partly (and unsatisfactorily) attainable with conventional latch devices, e.g. due to inaccuracies occurring in corresponding semi-conductor components during the manufacturing process.